Occurrence of chaotic behaviors because of fluctuations creation and their intensified transfer along the chain is one of the main causes of inefficiency of Material Requirements Planning (MRP) based supply chains. One of the reasons of the inefficiency is the lumpiness phenomenon. Through this phenomenon, some parts have an irregular production schedule, with nothing produced in some periods and large batches released in other periods. In this paper it is tried via the mathematical models to analyze this phenomenon. Using the mathematical deduction it is shown that the inventory fluctuations in upper levels of Bill of Material (BOM) in creation of lumpiness phenomenon are more effective than the inferior levels.